Because this piece has no abstract, we have provided for your benefit the first 3 sentences of the full text.

Sir: Nicotine abuse and dependence is a complex addictive
disorder with a pronounced genetic background. In addition, it
is one of the strongest risk factors for cardiovascular disorders
(CVD). It has been extensively discussed whether the known
high comorbidity between CVD and major depressive disorder
(MDD) is more likely determined by biological, such as genetic,
variables or by behavioral changes caused by depression,
which in turn enhance cardiovascular risks. Functional polymorphisms
of the angiotensin-converting enzyme (ACE) gene
are susceptibility factors for MDD.​